If There Was Only One...
The absolute reference in terms of tea shop is without a doubt Mariage Frères in Paris. They’re one of the oldest establishments in France and have done a lot to give tea it’s “lettres de noblesse”. They have, as only the French can do, made tea a luxury product. Their assortment is huge (600 varieties). They have published beautiful books on the subject. They have a range of perfumed candles and exquisite teaware. They even have a tea musem above their historic adress in the Marais (which is really worth a visit). They’re very expensive but you have the feeling of buying something precious. The staff, in colonial outfits, are very knowledgeable and one discovers something new every time. Mariage Frères is a bit the Hermès of tea : fabulous and very luxurious !!!
If you’re in Paris and you like tea, you MUST visit. The adress is : 30 rue du Bourg-Tibourg, Paris 4e Tél. : +33(0)1 42 72 28 11. I would advise not going on weekends as the Marais shop is quite small and it quickly gets very crowded (which detracts a lot from the experience).
Yixing (pronounced Yee-Shing) is a city in Jiangsu province in eastern China. It's very famous for it's reddish clay that has been used for centuries in teaware. It continues to be used today. The porous nature of the Yixing clay absorbs some of the tea aroma after each brew. Because of this, Yixing teapots are believed, over time, to enhance the flavor of the tea although to achieve this effect, one must always brew the same kind of tea in a specific teapot. This means that most people who use these teapots have several of them. For example, one for Ceylon, one for Darjeeling, one for Yunnan, one for Sencha etc... This tea enhancing property also explains their enduring popularity in China and now all over the world.
Sencha means common in Japanese. It's also their most common green tea. Which doesn't mean that it's not a good tea. The japanese are a very refined people when it comes to what they eat and drink. They take great care in buying (Sencha isn't cheap...), storing and brewing their tea. The local climate permits tea cultivation and tea has been a part of japanese culture at least since the ninth century when it was imported from China so most of Japan's production is consumed locally with little available for export. As such, Sencha, in our parts of the world, is something of a premium tea. 
There are four things that can harm tea: air, light, moisture, or excessive heat. Therefore to best protect your tea, store it in an air-tight, lightproof container away from moisture or heat. The foil bags that loose tea comes in, when you buy it at a good Tea shop, are good temporary storage containers. For longer term storage, the ideal container for Tea is the simple metal caddie with a narrow opening at the top (as illustrated).